A ball grid array (BGA) is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be put on a dual in-line or flat package. The whole bottom surface of the device can be used, instead of just the perimeter.

I need some advise from those with experience on this component. We are facing soldering problem "pillow effect"(from cross section result)on this BGA. In the reflow profile point of view which area should we focused more? The soak time or the Total Time above liquiduos? btw, we use SAC305 solderpaste. Thanks in advance for any input.